Detail here:
http://www.ft.com/intl/cms/s/0/5a5aa406-d33e-11e2-95d4-00144feab7de.html#axzz2WSPUoF1nLooks sensible, doesn't it? There's no change to the basic deposit guarantee: Depositors are already only protected up to 10 million yen (about $100 K USD). This is generally pretty well-known here, because several banks (including mine) went bust (and got nationalized) in the late 90s, and they temporarily removed the ceiling to guarantee all deposits, then put it back once the crisis was over. Both changes were big news at the time.
This proposal doesn't seem to change that - the idea is that banks can (must?) create a new kind of security that you can buy if you want to - effectively people would volunteer to insure them against running out of money. If you buy those securities and the bank is OK you'll make better returns than if you'd just been a regular depositor, but if the bank runs out of money (as judged by the regulators) you lose it all.
It sounds like everyone is going to do something like this, which will be much better than the status quo, where once the bank runs out of money either taxpayers or > 100K depositors get screwed.